Metabolic Phenotyping and Pharmacokinetics (MPPK) Core SUMMARY The MPPK Core will leverage a robust LC-MS/MS-based platform to: 1) Perform detailed pharmacokinetic (PK) studies of countermeasures; 2) Identify metabolic surrogates that track with the efficacy of countermeasures, as well as unanticipated off-target effects; 3) Identify very early markers of cyanide toxicity or persistent changes after prior transient exposure so that countermeasures can be instituted at the earliest possible juncture; 4) Identify the broad spectrum of metabolic derangements secondary to cyanide toxicity thus highlighting enzymes or metabolites for therapeutic intervention. For Project 1 (Hexachloroplatinate [HCP]), the Core will allow us to assess initial drug metabolism and pharmacokinetic (DMPK) attributes of platinum and related compounds under study. Further, because the platform is sensitive to pharmacological perturbations, studies of countermeasures in mammalian species may help us judge their relative safety and potential off-target effects. For Project 2 (Glyoxylate), the core will perform detailed PK studies of glyoxylate formulations and second generation glyoxylate derivatives. Additionally, metabolic tracing experiments focused on flux through lactate dehydrogenase (LDH) will enable the identification of complementary targets for countermeasure development. For Project 3 (Metabolic modulators), the core provides a particularly central support role given its focus on TCA cycle intermediates. Each of the aims proposes mechanistic metabolism studies that will heavily rely on the Core. These include the metabolic response to TCA cycle activators, one-carbon pathway agonists and other experimental therapeutics. The platform will also provide a more detailed understanding of the metabolic response to cyanide itself and how inhibition of Complex IV mediates that response. The MPPK Core will also provide synergy for other facets of our proposal, including iterative pharmacokinetic studies in conjunction with the Pharmaceutical Sciences Core. Thus, while the main goal of the platform will be to progress compounds along the therapeutic development pathway, our studies to date also highlight how the platform can provide additional scientific value. Embedded within our studies of interventions are clear opportunities to identify new diagnostic markers both of cyanide intoxication itself as well as effective rescue. A more complete understanding of the broad spectrum of metabolic derangements secondary to cyanide toxicity may highlight additional enzymes or specific metabolites that may be used as therapeutic interventions.